Model State Always true even when the required field is not sent - json

Question

I am simply calling an API and passing an object as a parameter and everything works fine. But then i wanted to validate the model before going any further so i simply wrote [Required] above the fields i always wanted filled.
MODEL
public class Consent
{
public Consent()
{
}
public int Id { get; set; }
[Required]
public int FacilityId { get; set; }
public string Heading { get; set; }
public string Description { get; set; }
}
and validate the model state in controller like this
public ActionResult<int> AddConsent(Consent consent)
{
if(!ModelState.IsValid){
throw new CustomException("000-0000-000", "Validation failed");
}
//Further Code
}
By this i expected model state to be false when i don't send the facilityId when i call the api
JSON
{
"heading": "HeadingFromPostman5",
"description": "DiscriptiomFromPostman5"
}
but its still true . I know .Net core is allocating 0 to int value when null but how can i validate it then? Whats the work around for this?

Answer 1

Simply replace this line:
[Required]
public int FacilityId { get; set; }
With this:
[Required]
public int? FacilityId { get; set; }

Answer 2

The Required attribute works well for nullable reference objects. For primitives, when an instance is created, the default value (in this case 0 for int) is assigned for FacilityId, and hence the Required won't work. If you make the FacilityId as nullable int then the Required attribute will work fine.
[Required]
public int? FacilityId { get; set; }